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// Copyright 2022 The OpenZipkin Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package grpc
import (
"context"
"github.com/openzipkin/zipkin-go/middleware"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/stats"
"github.com/openzipkin/zipkin-go"
"github.com/openzipkin/zipkin-go/model"
"github.com/openzipkin/zipkin-go/propagation/b3"
)
type serverHandler struct {
tracer *zipkin.Tracer
defaultTags map[string]string
baggage middleware.BaggageHandler
}
// A ServerOption can be passed to NewServerHandler to customize the returned handler.
type ServerOption func(*serverHandler)
// ServerTags adds default Tags to inject into server spans.
func ServerTags(tags map[string]string) ServerOption {
return func(h *serverHandler) {
h.defaultTags = tags
}
}
// EnableBaggage can be passed to NewServerHandler to enable propagation of
// registered fields through the SpanContext object.
func EnableBaggage(b middleware.BaggageHandler) ServerOption {
return func(h *serverHandler) {
h.baggage = b
}
}
// NewServerHandler returns a stats.Handler which can be used with grpc.WithStatsHandler to add
// tracing to a gRPC server. The gRPC method name is used as the span name and by default the only
// tags are the gRPC status code if the call fails. Use ServerTags to add additional tags that
// should be applied to all spans.
func NewServerHandler(tracer *zipkin.Tracer, options ...ServerOption) stats.Handler {
c := &serverHandler{
tracer: tracer,
}
for _, option := range options {
option(c)
}
return c
}
// HandleConn exists to satisfy gRPC stats.Handler.
func (s *serverHandler) HandleConn(_ context.Context, _ stats.ConnStats) {
// no-op
}
// TagConn exists to satisfy gRPC stats.Handler.
func (s *serverHandler) TagConn(ctx context.Context, _ *stats.ConnTagInfo) context.Context {
// no-op
return ctx
}
// HandleRPC implements per-RPC tracing and stats instrumentation.
func (s *serverHandler) HandleRPC(ctx context.Context, rs stats.RPCStats) {
handleRPC(ctx, rs)
}
// TagRPC implements per-RPC context management.
func (s *serverHandler) TagRPC(ctx context.Context, rti *stats.RPCTagInfo) context.Context {
md, ok := metadata.FromIncomingContext(ctx)
// In practice, ok never seems to be false but add a defensive check.
if !ok {
md = metadata.New(nil)
}
name := spanName(rti)
spanContext := s.tracer.Extract(b3.ExtractGRPC(&md))
// store registered baggage fields to be propagated in spanContext
if s.baggage != nil {
spanContext.Baggage = s.baggage.New()
for key, values := range md {
spanContext.Baggage.Add(key, values...)
}
}
span := s.tracer.StartSpan(
name,
zipkin.Kind(model.Server),
zipkin.Parent(spanContext),
zipkin.RemoteEndpoint(remoteEndpointFromContext(ctx, "")),
)
if !zipkin.IsNoop(span) {
for k, v := range s.defaultTags {
span.Tag(k, v)
}
}
return zipkin.NewContext(ctx, span)
}
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